/*
Copyright (c) 2019 Alibaba Group Holding Limited

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

*/
#include <stdlib.h>
//#include <serf/endian.h>
#include <math.h>
#include "minilibc_stdio.h"
/* convert double to string.  Helper for sprintf. */

static int copystring(char* buf,int maxlen, const char* s) {
  int i;
  for (i=0; i<3&&i<maxlen; ++i)
    buf[i]=s[i];
  if (i<maxlen) { buf[i]=0; ++i; }
  return i;
}
int __dtostr(double d,char *buf,unsigned int maxlen,unsigned int prec,unsigned int prec2) {
#if 1
  union {
    unsigned long long l;
    double d;
  } u = { .d=d };
  /* step 1: extract sign, mantissa and exponent */
  signed long e=((u.l>>52)&((1<<11)-1))-1023;
#else
#if (__cskyBE__)
  signed long e=(((*((unsigned long*)&d))>>20)&((1<<11)-1))-1023;
#else
  signed long e=(((((unsigned long*)&d)[1])>>20)&((1<<11)-1))-1023;
#endif
#endif
/*  unsigned long long m=u.l & ((1ull<<52)-1); */
  /* step 2: exponent is base 2, compute exponent for base 10 */
  signed long e10;
  /* step 3: calculate 10^e10 */
  unsigned int i;
  double backup=d;
  double tmp;
  char *oldbuf=buf;

  if ((i=__isinf(d))) return copystring(buf,maxlen,i>0?"inf":"-inf");
  if (__isnan(d)) return copystring(buf,maxlen,"nan");
  e10=1+(long)(e*0.30102999566398119802); /* log10(2) */
  /* Wir iterieren von Links bis wir bei 0 sind oder maxlen erreicht
   * ist.  Wenn maxlen erreicht ist, machen wir das nochmal in
   * scientific notation.  Wenn dann von prec noch was �brig ist, geben
   * wir einen Dezimalpunkt aus und geben prec2 Nachkommastellen aus.
   * Wenn prec2 Null ist, geben wir so viel Stellen aus, wie von prec
   * noch �brig ist. */
  if (d==0.0) {
    prec2=prec2==0?1:prec2+2;
    prec2=prec2>maxlen?8:prec2;
    i=0;
    if (prec2 && (long long)u.l<0) { buf[0]='-'; ++i; ++prec2;}
    for (; i<prec2; ++i) buf[i]='0';
    buf[buf[0]=='0'?1:2]='.'; buf[i]=0;
    return i;
  }

  if (d < 0.0) { d=-d; *buf='-'; --maxlen; ++buf; }

   /*
      Perform rounding. It needs to be done before we generate any
      digits as the carry could propagate through the whole number.
   */

  tmp = 0.5;
  for (i = 0; i < prec2; i++) { tmp *= 0.1; }
  d += tmp;

  if (d < 1.0) { *buf='0'; --maxlen; ++buf; }
/*  printf("e=%d e10=%d prec=%d\n",e,e10,prec); */
  if (e10>0) {
    int first=1;	/* are we about to write the first digit? */
    tmp = 10.0;
    i=e10;
    while (i>10) { tmp=tmp*1e10; i-=10; }
    while (i>1) { tmp=tmp*10; --i; }
    /* the number is greater than 1. Iterate through digits before the
     * decimal point until we reach the decimal point or maxlen is
     * reached (in which case we switch to scientific notation). */
    while (tmp>0.9) {
      char digit;
      double fraction=d/tmp;
	digit=(int)(fraction);		/* floor() */
      if (!first || digit) {
	first=0;
	*buf=digit+'0'; ++buf;
	if (!maxlen) {
	  /* use scientific notation */
	  int len=__dtostr(backup/tmp,oldbuf,maxlen,prec,prec2);
	  int initial=1;
	  if (len==0) return 0;
	  maxlen-=len; buf+=len;
	  if (maxlen>0) {
	    *buf='e';
	    ++buf;
	  }
	  --maxlen;
	  for (len=1000; len>0; len/=10) {
	    if (e10>=len || !initial) {
	      if (maxlen>0) {
		*buf=(e10/len)+'0';
		++buf;
	      }
	      --maxlen;
	      initial=0;
	      e10=e10%len;
	    }
	  }
	  if (maxlen>0) goto fini;
	  return 0;
	}
	d-=digit*tmp;
	--maxlen;
      }
      tmp/=10.0;
    }
  }
  else
  {
     tmp = 0.1;
  }

  if (buf==oldbuf) {
    if (!maxlen) {return 0;} --maxlen;
    *buf='0'; ++buf;
  }
  if (prec2 || prec>(unsigned int)(buf-oldbuf)+1) {	/* more digits wanted */
    if (!maxlen) {return 0;} --maxlen;
    *buf='.'; ++buf;
    prec-=buf-oldbuf-1;
    if (prec2) prec=prec2;
    if (prec>maxlen) return 0;
    while (prec>0) {
      char digit;
      double fraction=d/tmp;
      digit=(int)(fraction);		/* floor() */
      *buf=digit+'0'; ++buf;
      d-=digit*tmp;
      tmp/=10.0;
      --prec;
    }
  }
fini:
  *buf=0;
  return buf-oldbuf;
}
